This invention relates to tuning systems for broadcast television signals. More particularly, this invention relates to worldwide tuning systems that are configurable to various broadcast television standards and channel frequencies used throughout the world.
Analog video standards for broadcast television differ from country to country. The broadcast television standard used here in the United States, for example, is different than the broadcast standard used in France. Conventional standards include multiple versions of NTSC (National Television Standards Committee), multiple versions of PAL (Phase Alternate Line), and multiple versions of SECAM (Sequential Couleur Avec Memoire).
Broadcast frequencies also change from country to country. Each country is assigned a range of frequencies to allot to its domestic television broadcast service. An international governing body known as the xe2x80x9cInternational Telecommunications Unionxe2x80x9d or xe2x80x9cITUxe2x80x9d governs the allocation of broadcast frequencies among the various countries.
The country-by-country discrepancies among broadcast standards and channel frequencies pose a problem for television manufacturers. Since each country employs a particular standard and operates within a particular range of frequencies, manufacturers must tailor their televisions to the country into which they are to be sold. Traditionally, the manufacturers have hardwired the televisions during manufacturing to comply with the standard and frequency requirements of the destination country.
FIG. 1 shows the hardware components of a broadcast television 20. It includes a tuner 22, a crossbar 24, a video decoder 26, a display 28, and speaker(s) 30. The tuner 22 tunes to a particular channel frequency to receive a broadcast television signal, which carries both video and audio data. The tuner 22 separates an analog video signal from an analog audio signal. The crossbar 24 routes the analog video signal to the video decoder 26, which converts the analog video signal to digital video data used to drive the display 28. The crossbar 24 also routes the analog audio signal to the speaker(s) or other audio components 30. It is noted that FIG. 1 represents a more modern television, which has digital capabilities. In older televisions, the crossbar 24 routes the analog video signal directly to the display 28 for depiction.
Under conventional manufacturing techniques, televisions used in different countries have different tuners 22 and video decoders 26. Televisions shipped in the United States are equipped with tuners and video decoders compatible with the U.S. broadcast standards and frequencies, whereas televisions shipped to other countries are equipped with different tuners and video decoders that are compatible with their broadcast standards and frequencies.
Country-based customization is inefficient because the manufacturer must make several versions of a product. In addition to broadcast standards and frequencies, the manufacturer might also have to contend with other regional differences, such specialized audio decoders for a particular market, or variations in picture tubes (e.g., 525 v. 625 line operation). The customization plays havoc with inventories because an overabundance of televisions for one country may not be cross-sold into another country where demand is strong.
To partially address this problem, manufacturers began using tuners and decoders that support multiple standards and frequencies. With this improvement, manufacturers are able to mass-produce one version of the television using the same components regardless of the destination country. Prior to shipping, the manufacturers program the tuner and decoder at the factory to a desired television standard and frequency range for the destination country.
While this is an improvement, it is not ideal. Video standards employed within a country may change. A country might decide to reallocate the broadcast frequencies, or perhaps adopt a different television standard, for political, administrative, or technical reasons. Televisions programmed at the factory are not capable of accommodating these changes. Accordingly, there is a need to design a television tuning system that may be upgraded in the field.
Another problem concerns portability. In the past, televisions sold into one country would typically reside in that country for the life of the product. It was less common for people to transport their televisions to different countries, unless they were permanently moving.
Today, as television tuner hardware decreases in size and continues to fall in component cost, it can be incorporated into portable computing devices, such as laptop computers. Given the portable nature of these computing devices, it is very likely that they will be used in numerous different locations throughout the world that employ different television standards and channel frequencies. Thus, there is a need for a worldwide television tuning system that is reconfigurable in the field to adapt to different television standards and channel frequencies.
This invention concerns a worldwide tuning system that may be implemented in televisions, computing devices, or other television broadcast receiving units. The worldwide tuning system is configurable to the television standards and channel frequencies of multiple different countries, and is reconfigurable in the event any of these parameters change. As a result, the worldwide tuning system may be transported to different countries and reconfigured to local television broadcasts. Additionally, the worldwide tuning system is upgradable in the field to accommodate any changes in television standards and channel frequencies used in various countries.
The worldwide tuning system is configurable based on a country""s ITU long-distance country code. The tuning system maintains a country code table listing a plurality of countries according to their ITU codes. For instance, the United States has an ITU code of 1 and France has an ITU code of 33. The tuning system also maintains multiple channel-to-frequency mapping tables that provide television standards and correlate channel numbers to corresponding frequencies for associated countries in the country table. The country table indexes the channel-to- frequency mapping tables.
During configuration, a user or application selects a particular country by passing in the ITU code. The tuning system uses the ITU code to locate an entry for that country in the country code table. The table entry contains an index to an associated channel-to-frequency mapping table for the selected country. The tuning system then loads and saves the channel-to-frequency mapping table for subsequent use until a new and different ITU code is passed in. The tuning system utilizes the television standard listed in the channel-to-frequency mapping table for decoding broadcast television signals in the selected country.
During tuning, the user or application enters a particular channel number. The tuning system uses the channel number to lookup a corresponding television frequency in the channel-to-frequency table. The tuning system then tunes to the television frequency.
In one implementation, the television tuning system is configured in a hardware/software architecture with parallel hardware and software components. The hardware components include tuner circuitry to tune to various television frequencies carrying television video signals and video decoder circuitry coupled to receive a television video signal from the tuner circuitry and to convert the television video signal to digital video data. Audio decoder circuitry may also be incorporated to decode the audio portion of the television signal.
The software components include a tuner module coupled to adjust the tuner circuitry to a particular television frequency and a video decoder module to decode the digital video data according to a particular video standard. The software layer also includes an audio module for controlling the audio decoder circuitry and one or more VBI (vertical blanking interval) modules for processing VBI data contained in the television signal. A driver interface layer interfaces the software layer and the hardware circuitry.
When a new channel is requested, the tuner module generates and sends a beginning tuning packet to inform the video decoder module and other downstream modules of an impending change to the new channel. The tuner module then controls the tuner circuitry to tune to a new television frequency that corresponds to the new channel. Afterward, the tuner module generates and sends an ending tuning packet to inform the video decoder module and other downstream modules that the channel change is complete. The tuning packet includes a designation of country within which the tuning system is configured to receive television signals, a channel to be tuned, the particular video standard, and flags indicating whether the tuning packet represents a beginning of a tuning operation or an ending of the tuning operation.
In the interim between the beginning and ending tuning packets, some of the modules may temporarily cease processing the television signal to avoid processing contaminated or incomplete data resulting from the channel change operation. For instance, the audio module might mute the audio playback and the VBI modules might stop processing the VBI data while the channel is being changed.